Conventionally, the known methods for producing 1,2-benzisothiazoles and 3-halo-1,2-benzisothiazoles include the following:
(A) Ann. Chim. (Rome) 53(5), 577-87(1963) ##STR1##
However, the above known methods have the following drawbacks:
In (A) and (B), examples of methods for producing 1,2-benzisothiazoles are disclosed. Since there are no disclosures concerning a method by which 2-substituted benzaldehyde oximes, the starting materials, can be obtained on an industrial scale, details are unknown. Also, the yields by these methods are not high.
In (C) and (D), examples of methods for producing 3-chloro-1,2-benzisothiazoles are disclosed. The method of (C) uses expensive 1,2-benzisothiazol-3-ones as the starting materials, and gives a poor yield. The method of (D) cannot be said to be industrially advantageous because this method requires the use of expensive thiosalicylic acid as the starting material and achieves an unsatisfactory yield.
As mentioned above, with any known methods, it has been difficult to advantageously produce 1,2-benzisothiazoles and 3-halo-1,2-benzisothiazoles on an industrial scale.